Embodiments of the present invention relate to printing apparatus and to printing systems.
Thermal transfer printing apparatus, such as thermal transfer overprinters (TTOs), are well known. Thermal transfer printing apparatus typically use a ribbon (aka tape) coated with a layer of ink, to transport the ink required for a printing operation. A printhead presses the inked ribbon against a target printing substrate before heating elements within the printhead are activated to melt the ink on the ribbon and cause its transfer to the target substrate. As the printhead and the substrate are moved relative to one another selected printhead heating elements are activated to create a desired image on the substrate.
It is known to provide thermal transfer printing apparatus in two different operational configurations. In the first, so called “intermittent”, configuration the substrate to be printed and the ribbon are held stationary during a printing operation, whilst the printhead is moved across the surface of the substrate.
At the start of a printing operation the printhead moves towards a support (typically a flat platen) with the ribbon and substrate sandwiched therebetween. The printhead is then moved across the platen and whilst doing so ink from the ribbon is transferred to the substrate. Once the printing operation is complete, the printhead is lifted away from the platen and returned to its start position, whilst the ribbon and substrate are advanced in anticipation of the next printing operation.
In the second, so called “continuous” configuration, the substrate to be printed moves substantially continuously past a printing point.
The ribbon is accelerated to match the speed of the substrate before the printhead is moved towards a support (typically a roller) with the ribbon and substrate sandwiched therebetween. As the printhead presses the ribbon against the substrate a printing operation is carried out which causes transfer of ink from the ribbon to the substrate.
FIG. 1 is a schematic diagram of a prior art thermal transfer overprinter 10. The TTO 10 is typically formed of two main component parts: a cassette and a casing. The cassette supports supply and take-up spools 2, 3 and the casing houses components of the TTO 10. A ribbon 5 is fed from the supply spool 2 to the take up (or waste) spool 3. The ribbon 5 is guided between the spools by fixed rollers 1 past a printhead 4. A target substrate 7 passes over a platen 6. The printhead 4 can move to press the moving ribbon against the target substrate 7.
It is well known in the industry to use a cassette to support the ribbon spools 2, 3. The mechanical precision of the cassette is intrinsic to the smooth operation of the printer. The spools have to be held parallel and aligned to each other and any intervening rollers 1. This ensures that the ribbon 5 passes accurately from the supply spool 2 to the take-up spool 3, for example without creasing or wrinkling.
The TTO 10 also includes the casing which accommodates components such as one or more motors for rotatably driving the spools 2, 3, the printhead 4, one or more printed circuit boards and the like. In all known instances, the casing and cassette are machined from tool grade aluminium.